I am no Sparkie however on my truck a have a 24V to 12V voltage reducer fitted which feeds to a Redarc Charger mounted inside of the chassis rail at the rear which feeds to the Anderson plug to charge van batteries whilst driving. Two 110 amp deep cycle batts, solar power on van and 1800w Inverter.
Well 700watts of solar is over 60 amps by its self ,so maybe have two controllers one to control the solar at 60+ amps and the other from the alternator . Keeping in mind the capabilities of the alternator .and I don't know it's output current .can't see the connection of the alternator being any concern but mainly the current capability,interesting thought though, but if you are going to do that why not a 24/12 DC DC charger.
Is it possible to feed 24v from my truck alt straight into a 60amp MPPT
along with 600-750 watts of solar panels and 12v flowing out the other side?
In a word, NO. MPPT controllers regularly test the solar array to check its capability at the time of the check (remember solar panel capabilities can change change regularly during thetime of day and amount of cloud.) There are three scenarios.
1. If you have configured your array as a 12 V array then the controller will most probable set itself up for a very high input voltage that will be higher then the array open circuit output voltage. In that case your array will cease contributing.
2. If you have configured your panels into a higher voltage array then the array will feed the 24 V batteries and take over from the engine alternator. When the 24 V system voltage rises to a level higher than the normal regulation voltage, the alternator regulator will cut back the alternator output. The array may then be the predominant system contributor. With the amount of solar capacity it could possibly take over completely.
3. Your MPPT controller may not be capable of working as I described and anything could happen to the controller or 24 V system.
Get yourself a DC-DC charger that is capable of charging a 12 V battery from a 24 V alternator/battery system. Connect it to your house battery in parallel with solar system. This could upset any battery capacity monitoring that may be built into your controller so you will have to ass a separate battery monitor.
-- Edited by PeterD on Monday 14th of September 2015 09:25:20 AM
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PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
We currently have a 24v Coaster bus 80amp alternator with 2 way VSR, 580w of solar at 24v that feeds a 24v house pair & top up the start battery's if they need it, they then feed via a Redark 24 to 12v 30a DC to DC charger to the single 120ah 12v house battery.
Compressor fridge & invertor run off 24v as I have 300ah available, rest of the house runs 12v & never have an issue, even run the split air-con on the inverter if needed.
Worth spending the bucks on good gear to have a hassle free journey.
Keep it simple, more rotating parts mean more issues at some stage.
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Looks like an easy and effective way to get the job done but $450 and i will still need 240v charger.
KTM
The Redarc BCDC1240 will happily accept up to 32v DC input and output 12v 3-stage charge, also included in the package is a 40A MPPT solar regulator.
I have read on a forum of using the mppt input fed from a suitable 240v/13.8 v power supply of equivalent capacity, so you do not then need a 240vac charger.
But the unit would perform well as designed with a decent solar array making a 240v charger unnecessary. By the way the retail on the Redarc is $740 so $450 is a good deal.
I am currently in the planning process of building a truck based motorhome on an Isuzu nps 300 4x4 chassis cab, and will be using one of these myself.
Looks like an easy and effective way to get the job done but $450 and i will still need 240v charger.
KTM
The Redarc BCDC1240 will happily accept up to 32v DC input and output 12v 3-stage charge, also included in the package is a 40A MPPT solar regulator.
I have read on a forum of using the mppt input fed from a suitable 240v/13.8 v power supply of equivalent capacity, so you do not then need a 240vac charger.
But the unit would perform well as designed with a decent solar array making a 240v charger unnecessary. By the way the retail on the Redarc is $740 so $450 is a good deal.
I am currently in the planning process of building a truck based motorhome on an Isuzu nps 300 4x4 chassis cab, and will be using one of these myself.
Yeah i see it has an onboard MPPT how many watts of panels will it take?
At this stage i think 3x200w 12v panels with 440amps of batteries going to be enough for what i need was originally going a lot more but now think it may be overkill.
I started on my truck only 7 weeks ago and knew nothing about caravanning have learned a lot on the way,, i thought i may get it all done for about 5k at the start haha!
My truck only owed me 17k and i know it well after 2 years I've owned it my new fit out budget is 15k. It only took me one week in to start wanting a 4x4 chassis but theres always a next time
IMO you can never have too much solar, the limit is usually regulated by roof space available anyway. I know of a couple with over a kw of panels on their RV !
You can have too many LA batteries though as again IMO, more than two in parallel is a recipe for disaster.
In my new rig I will move to Lifpo4 with my new outfit as even though initially expensive to set up they are a far better prospect to AGM batteries, with a much better life expectancy.
